Adsorption separation of sterols from tall oil pitch with carbon adsorbent

Abstract

An adsorptive separation process for separating sterols from a tall oil feed mixture, which process comprises contacting the feed mixture with an adsorbent comprising a carbon sieve having average pore diameters greater than about 20 Å, especially 30-90 Å, and a surface area greater than about 300 m 2 /g, especially 700-1100 m 2 /g, and, preferably, a carbonaceous pyropolymer or carbonized resin, selectively adsorbing substantially all of the sterols to be separated to the substantial exclusion of the other components and thereafter recovering high purity sterols. A desorption step is used to desorb the adsorbed sterols with an aromatic liquid hydrocarbons, e.g., toluene or chlorobenzene.

What is claimed is: 
     
       1. A process for separating sterols from a tall oil feed mixture, which process comprises contacting at adsorption conditions said mixture with an adsorbent comprising a synthetically-derived, non-activated porous carbon sieve having pore diameters greater than 15 A and surface area greater than 300 m 2  /g, selectively adsorbing said sterols to the substantial exclusion of other components of the tall oil feed, and treating said adsorbent containing said sterols with a desorbent material comprising an aromatic liquid hydrocarbon to desorb said sterols therefrom as a fluid extract stream. 
     
     
       2. The process of claim 1 further characterized in that said desorbent is selected from the group consisting of toluene, tetralin, chlorotoluene, anisol, mesitylene, chlorobenzene, benzyl alcohol and 1-methyl-naphthalene. 
     
     
       3. The process of claim 2 wherein said sterols comprise β-sitosterol. 
     
     
       4. The process of claim 2 wherein said sterol comprises cholesterol. 
     
     
       5. The process of claim 1 further characterized in that said adsorption conditions include a temperature within the range of from about 20° C. to about 230° C. and at a pressure within the range of from about atmospheric to about 500 psig. 
     
     
       6. The process of claim 1 wherein said adsorbent is a carbonaceous pyropolymer. 
     
     
       7. The process of claim 1 wherein said adsorbent is a carbonized resin. 
     
     
       8. The process of claim 1 wherein said pore diameter is from about 20 A to about 90 A. 
     
     
       9. The process of claim 8 wherein said surface area is from about 700 m 2  /g to about 900 m 2  /g. 
     
     
       10. The process of claim 1 wherein said desorbent is chlorobenzene. 
     
     
       11. The process of claim 1 wherein said desorbent is toluene. 
     
     
       12. A process for separating sterols from a tall oil feed mixture which process comprises contacting at adsorption conditions said mixture with an adsorbent comprising a porous carbon sieve having pore diameter greater than 20 Å and a surface area greater than about 300 m 2  /g, which process comprises the steps of: (a) maintaining net fluid flow through a column of said adsorbent in a single direction, which column contains at least three zones having separate operational functions occurring therein and being serially interconnected with the terminal zones of said column connected to provide a continuous connection of said zones;   (b) maintaining an adsorption zone in said column, said zone defined by the adsorbent located between a feed inlet stream at an upstream boundary of said zone and a raffinate outlet stream at a downstream boundary of said zone;   (c) maintaining a purification zone immediately upstream from said adsorption zone, said purification zone defined by the adsorbent located between an extract outlet stream at an upstream boundary of said purification zone and said feed inlet stream at a downstream boundary of said purification zone;   (d) maintaining a desorption zone immediately upstream from said purification zone, said desorption zone defined by the adsorbent located between a desorbent inlet stream at an upstream boundary of said zone and said extract outlet stream at a downstream boundary of said zone;   (e) passing said feed stream into said adsorption zone at adsorption conditions to effect the selective adsorption of said sterols by said adsorbent in said adsorption zone and withdrawing a raffinate outlet stream from said adsorption zone;   (f) passing a desorbent material into said desorption zone at desorption conditions to effect the displacement of said sterols from the adsorbent in said desorption zone, said desorbent material comprising a liquid aromatic hydrocarbon;   (g) withdrawing an extract stream comprising said sterols and desorbent material from sad desorption zone;   (h) periodically advancing through said column of adsorbent in a downstream direction with respect to fluid flow in said adsorption zone the fee inlet stream, raffinate outlet stream, desorbent inlet stream, and extract outlet stream to effect the shifting of zones through said adsorbent and the production of extract outlet and raffinate outlet streams.   
     
     
       13. The process of claim 12 further characterized in that said desorbent material comprises toluene. 
     
     
       14. The process of claim 12 further characterized in that said desorbent comprises chlorobenzene. 
     
     
       15. The process of claim 12 further characterized in that it includes the step of maintaining a buffer zone immediately upstream from said desorption zone, said buffer zone defined as the adsorbent located between the desorbent input stream at a downstream boundary of said buffer zone and a raffinate output stream at an upstream boundary of said buffer zone. 
     
     
       16. The process of claim 12 further characterized in that said adsorption conditions and desorption conditions include a temperature within the range of from about 20° C. to about 230° C. and a pressure within the range of from about atmospheric to about 500 psig. 
     
     
       17. The process of claim 12 wherein said sterols comprise β-sitosterol. 
     
     
       18. The process of claim 12 wherein said sterols comprise cholesterol. 
     
     
       19. The process of claim 12 wherein said adsorbent is a carbonaceous pyropolymer. 
     
     
       20. The process of claim 12 wherein said adsorbent is a carbonized resin.